IN HOC SIGNO VINCES

18-year-old man arrested Saturday in connection with terror attack on London tube. ISIS has claimed responsibility for the attack. An apparent bucket-bomb explosion rocked a London subway train Friday morning. The terror attack is the sixth in Britain this year. The blast sent 29 people to the hospital. A manhunt is underway for perpetrators, with no arrests yet. The threat level has been raised to “critical,” meaning an attack is expected imminently. Witnesses described a ball of flames and a loud explosion. Police said the improvised explosive device used did not fully explode. _______________________________________________________________

An 18-year-old man was arrested Saturday morning in Dover, England, in connection with Friday’s London subway terror attack, which ISIS has claimed responsibility, police announced.

The man, apprehended by Kent Police in Dover’s port area, was arrested under section 41 of the U.K.’s Terrorism Act, London Metropolitan Police said in a statement. The man remains in custody at a local police station. He will be transferred to a south London police station.

“We have made a significant arrest in our investigation this morning,” Deputy Assistant Commissioner Neil Basu, Senior National Co-ordinator for Counter Terrorism Policing, said. “Although we are pleased with the progress made, this investigation continues and the threat level remains at critical.”

Basu added, ““This arrest will lead to more activity from our officers. For strong investigative reasons we will not give any more details on the man we arrested at this stage.”

London mayor Sadiq Khan said in a statement following the arrest, “The police investigation is ongoing and there will still be significant activity today and over the days ahead. I am sure I speak for London when I say we are incredibly grateful to the police and intelligence services for doing everything possible to keep Londoners safe.”

ISIS claimed responsibility for the attack through its propaganda news agency, Amaq.

A manhunt kicked off after an apparent bucket bomb exploded on a subway train during rush hour Friday, sending a fireball through the passenger car and sending at least 29 people to the hospital, officials said.